The 2014 elections probably won’t have any effect on the 2016 presidential contest, but they will have an effect on that year's congressional races. The Republicans will have more incumbents in the House, making their majority highly likely to survive even a good Democratic year. And in the Senate, while the map will strongly favor Democrats, Republicans will have some capacity for absorbing losses.

That’s very good news for Republicans. It gives them an excellent opportunity to achieve unified government in 2017, while Democrats have only the slimmest chance of doing so. And it’s not just in 2017. The senators elected this year will be in place for six years, and in the House, the incumbency advantage means that some of the 2014 pick-ups will keep their seats for a long time. Reversals are possible – just ask the Democrats, who had large majorities after their back-to-back landslides in 2006 and 2008. But for parties, it's always better to have more seats.

There is, however, a potential paradox: Republicans are extremely unlikely to add significantly to their majorities, even if they have a good year in 2016. There just aren’t a lot of vulnerable Democratic seats remaining in the House, and in the Senate, the playing field will be as bad next time as it was good this time.

What this means is that if a Republican wins the presidency (and consider that race a toss-up so far, as I’ve been saying), he or she won’t be entering office with very many new Republicans. That’s potentially important, because very few Republicans are going to feel they owe their seats to the White House. Presidents elected in those conditions -- John Kennedy, Jimmy Carter and Bill Clinton -- tend to have less influence over their congressional parties than those such as Ronald Reagan and Barack Obama who bring plenty of friendly new faces with them.

On the other hand, if 2016 turns out to be a good Democratic year, the new president will probably have relatively long coattails, and could be more influential with his party on the Hill.

So the 2014 elections, while a victory for Republicans, could weaken a Republican president or strengthen the next Democratic one. Not that this is something partisans would worry about -- if anything, conservative activists would probably rather see their influence move from the Oval Office to Congress during unified Republican government.

This column does not necessarily reflect the opinion of Bloomberg View's editorial board or Bloomberg LP, its owners and investors.